I teach in a Japanese High School (40 kids a class!) and the levels of the kids are varied - some really low and some not so low! I recently came across a text called Topic Talk Issues published by EFL Press in Japan and it is a wonderful textbook. The topics are really interesting and there are a lot of good ideas in it. It focuses on Japanese EFL students and speaking. My partner also uses it for teaching his private adult students. If you have a chance, take a look at it! Good luck.